From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 74805 invoked by alias); 6 Dec 2015 02:35:17 -0000 Mailing-List: contact cygwin-help@cygwin.com; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: cygwin-owner@cygwin.com Mail-Followup-To: cygwin@cygwin.com Received: (qmail 74648 invoked by uid 89); 6 Dec 2015 02:34:48 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-0.6 required=5.0 tests=AWL,BAYES_05,FREEMAIL_ENVFROM_END_DIGIT,FREEMAIL_FROM,RCVD_IN_DNSWL_LOW,SPF_PASS autolearn=ham version=3.3.2 X-HELO: mail-wm0-f45.google.com Received: from mail-wm0-f45.google.com (HELO mail-wm0-f45.google.com) (74.125.82.45) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (AES128-GCM-SHA256 encrypted) ESMTPS; Sun, 06 Dec 2015 02:34:46 +0000 Received: by wmec201 with SMTP id c201so122156969wme.0 for ; Sat, 05 Dec 2015 18:34:43 -0800 (PST) MIME-Version: 1.0 X-Received: by 10.28.214.143 with SMTP id n137mr13834806wmg.2.1449369282971; Sat, 05 Dec 2015 18:34:42 -0800 (PST) Received: by 10.27.87.195 with HTTP; Sat, 5 Dec 2015 18:34:42 -0800 (PST) In-Reply-To: <566367C8.5020703@maxrnd.com> References: <564E3017.90205@maxrnd.com> <5650379B.4030405@maxrnd.com> <20151121105301.GE2755@calimero.vinschen.de> <5652C402.7040006@maxrnd.com> <24780-1448274431-7444@sneakemail.com> <5653B52B.5000804@maxrnd.com> <20151126093427.GJ2755@calimero.vinschen.de> <5656DDEF.9070603@maxrnd.com> <5662C199.7040906@maxrnd.com> <566367C8.5020703@maxrnd.com> Date: Sun, 06 Dec 2015 02:35:00 -0000 Message-ID: Subject: Re: Cygwin multithreading performance From: Kacper Michajlow To: cygwin@cygwin.com Content-Type: text/plain; charset=UTF-8 X-IsSubscribed: yes X-SW-Source: 2015-12/txt/msg00058.txt.bz2 2015-12-05 23:40 GMT+01:00 Mark Geisert : > Kacper Michajlow wrote: >> >> 2015-12-05 11:51 GMT+01:00 Mark Geisert : >>> >>> Mark Geisert wrote: >>> In the OP's very good testcase the most heavily contended locks, by far, >>> are >>> those internal to git's builtin/pack-objects.c. I plan to show actual >>> stats >>> after some more cleanup, but I did notice something in that git source >>> file >>> that might explain the difference between Cygwin and MinGW when running >>> this >>> testcase... >>> >>> #ifndef NO_PTHREADS >>> >>> static pthread_mutex_t read_mutex; >>> #define read_lock() pthread_mutex_lock(&read_mutex) >>> #define read_unlock() pthread_mutex_unlock(&read_mutex) >>> >>> static pthread_mutex_t cache_mutex; >>> #define cache_lock() pthread_mutex_lock(&cache_mutex) >>> #define cache_unlock() pthread_mutex_unlock(&cache_mutex) >>> >>> static pthread_mutex_t progress_mutex; >>> #define progress_lock() pthread_mutex_lock(&progress_mutex) >>> #define progress_unlock() pthread_mutex_unlock(&progress_mutex) >>> >>> #else >>> >>> #define read_lock() (void)0 >>> #define read_unlock() (void)0 >>> #define cache_lock() (void)0 >>> #define cache_unlock() (void)0 >>> #define progress_lock() (void)0 >>> #define progress_unlock() (void)0 >>> >>> #endif >>> >>> Is it possible the MinGW version of git is compiled with NO_PTHREADS >>> #defined? If so, it would mean there's no locking being done at all and >>> would explain the faster execution and near 100% CPU utilization when >>> running under MinGW. >> >> >> Nah, there is no threading enabled when there is no pthreads. How >> would that work? :D See thread-utils.h >> >> #ifndef NO_PTHREADS >> #include >> >> extern int online_cpus(void); >> extern int init_recursive_mutex(pthread_mutex_t*); >> >> #else >> >> #define online_cpus() 1 >> >> #endif > > > We're not familiar at all with MinGW. Could you locate the source for > MinGW's pthread_mutex_lock() online and give us a link to it? And BTW, > which Windows are you running and on what kind of hardware (bitness and > #CPUS/threads)? > > It looks like we're going to have to compare actual pthread_mutex_lock() > implementations. Inspecting source is nice but I don't want to be chasing a > mirage so I really hope there's a pthread_mutex_lock() function inside the > MinGW git you are running. gdb could easily answer that question. Could > you please do an 'info func pthread_mutex_lock' after starting MinGW git > under MinGW gdb with a breakpoint at main() (so libraries are loaded). > > > ..mark > > > -- > Problem reports: http://cygwin.com/problems.html > FAQ: http://cygwin.com/faq/ > Documentation: http://cygwin.com/docs.html > Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple > Hmm, thinking about it mingw doesn't have pthread implementation or any wrapper for it. If someone needs pthread they would probably go for pthreads-w32 implementation. I started to wonder because I don't recall git would need pthreads to compile on Windows. And indeed they have a wrapper for Windows API... https://github.com/git/git/blob/master/compat/win32/pthread.h https://github.com/git/git/blob/master/compat/win32/pthread.c Though it is not really a matter that "native" git build is fast and all, but that Cygwin's one really struggles if it comes to MT workload . And this not only issue with git unfortunately. Download speeds are also limited on Cygwin. I know POSIX compatibility layers comes with a price but I would love to see improvements in those areas. Cygwin: Receiving objects: 100% (230458/230458), 78.41 MiB | 1.53 MiB/s, done. "native" git: Receiving objects: 100% (230458/230458), 78.41 MiB | 18.54 MiB/s, done. I'm on Windows 10 x64 and i7 5820K (6C/12T). -Kacper -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple